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The 20/20 Myth
The 20/20 designation of how clearly you see is simply a measure of how small a letter you can see from 20 feet away. The chart we use to measure this was devised by Herman Snellen in the mid 1800's, and is commonly called the Snellen chart. Most people think that if you can read this small row of letters and thus are deemed to have 20/20 vision, that you have perfect vision. This is not true. The measure of visual acuity is only one aspect of how well we see. There are, in fact, many other aspects of vision to consider such as peripheral vision, depth perception, coordination of the eyes, eye-hand coordination, and visual processing or perceptual skills.
In order for our brain to gather visual information from our environment, we first have to be able to move our eyes and hold them steady, adjust our focusing muscles for that distance, and aim each eye at the same location. This enables us to see clearly, keep our eyes on a target, see the three dimensional world, and judge where our target is. The visual system is also responsible for piloting us through the environment.
When your child passes the vision screening, almost always the Snellen Test, at school or the pediatrician, know that they have good distance vision clarity, but be aware that this test does not tell you about the basic visual skills, and processing of visual information. There may still be delays in the development of visual skills which make it difficult to keep their place when reading, or create strain in looking at the printed page. Likewise, the Snellen Test does not tell you about how well the brain coordinates the eyes in order to catch or hit a ball.
When your child passes the vision screening, almost always the Snellen Test, at school or the pediatrician, know that they have good distance vision clarity, but be aware that this test does not tell you about the basic visual skills, and processing of visual information. There may still be delays in the development of visual skills which make it difficult to keep their place when reading, or create strain in looking at the printed page. Likewise, the Snellen Test does not tell you about how well the brain coordinates the eyes in order to catch or hit a ball.
Scientists tell us that the information from the eye goes to at least 40 different areas of the brain, but the designation of 20/20 only tells us how well a couple of those circuits are working. Eye doctors recommend that children have a comprehensive vision exam before starting school and every year while in school, since 80% of what we learn comes in through the visual system, and their vision can change dramatically from year to year. This comprehensive exam should include testing for clarity of vision, refraction (measure for the need of glasses), eye health, and basic eye coordination skills (eye teaming, eye movements, and focusing). When there are concerns about catching a ball or handwriting, eye hand coordination can be tested. If there are concerns about learning, visual perceptual skills such as visual memory, visualization, and reversals, can be tested.
So when your child passes the school vision screening with or without glasses, remember that this only tells you about their eye sight at distance. Annual visits to the eye doctor are still recommended to ensure that visual skills are developing properly, so that learning can occur unhindered by weak or delayed visual skills.